Chemistry Reference
In-Depth Information
þ
8AuSR
!
Au
20
S
ð
8
Au
2
S
ð
3
4
Au
28
S
ð
20
:
Au
20
S
ð
12
The SR ligands bridge pairs of metal atoms and the [Au
2
(SR)
3
] ligands bridge
non-adjacent metal atoms on folded diamonds of Au
4
made from two adjacent faces
as shown in Fig.
26
. The stoichiometric and structural relationships for these
clusters are summarised in Table
1
.
3.7.3 Alternative Geometries
The same principles may be applied to the recently reported [Au
14
(PPh
3
)
8
(NO
3
)
4
],
which has two trigonal-bipyramidal Au
5
fragments directly connected by a short
Au-Au bond (2.651
), and this bond also has a collar of 4 AuNO
3
leading to an
ellipsoidal shape and a polyhedron having triangular faces (see II).
Au
14
PPh
3
Å
Þ
8
NO
3
4
Au
14
L
12
4
þ
Au
14
SR
6
2
Au
14
Au
SR
2
6
2
ð
Au
14
Au
2
S
ð
3
6
2
:
This leads to the prediction of three homoleptic possibilities, viz. [Au
14
(SR)
6
]
2
,
[Au
20
(SR)
12
]
2
or [Au
26
(SR)
18
]
2
or mixed species. All would share in common a
pair of interstitial atoms inside a 12-atom polyhedron.
The same principles may be applied to other classes of clusters in Fig.
22
. For
example, toroidal or oblate clusters are characterised by [S
σ
]
2
[P
σ
]
4
and are exem-
plified by [Au
9
(PPh
3
)
8
]
3+
and [Au
10
Cl
3
(PCy
2
Ph)
6
]
+
and lead to the following
homoleptic replacement series:
Au
9
PPh
3
Þ
8
3
þ
Au
9
SR
4
Au
9
Au
SR
2
4
ð
Au
9
Au
2
S
ð
3
4
Au
13
SR
8
Au
17
SR
12
:
Au
10
Cl
3
PCy
2
Ph
Þ
6
þ
Au
10
SR
5
Au
10
Au
SR
2
5
ð
Au
10
Au
2
S
ð
3
5
Au
5
SR
10
Au
20
SR
15
:
The analysis may also be used to provide an insight into structures which have
been calculated from DFT calculations. For example, [Au
18
(SR)
14
] has two tetra-
hedral Au
4
moieties (which are characterised by [S
σ
]
2
) which are well separated and
with two pairs of [Au
2
(SR)
4
] and [Au
2
(SR)
3
] staple ligands [
109
]:
2
þ
2Au
4
S
ð
2
2Au
4
PPh
3
ð
Þ
4
Au
3
S
ð
4
Au
18
S
ð
14
:
2Au
4
Au
2
S
ð
3
The analysis above has underlined in a very transparent manner the structural
relationships between phosphine and organothiolato-cluster compounds, which has
been proposed previously by H¨kkinen.
